1. Field of the Invention
The present invention relates to a method for producing a polymer composition that is used in wide varieties of applications such as general consumer products, industrial products and foods and also to a production apparatus by the method.
The present invention relates to a polymer composition containing a polyphenylene sulfide resin superior in toughness such as impact strength and tensile elongation and a molded article produced by using the polymer composition, which can be used widely in various fields such as electric and electronic parts, auto-parts, and general mechanical parts.
The present invention relates to an electrophotographic transferring belt and an image-forming apparatus having equipped with the transferring belt.
2. Description of the Related Art
Polyphenylene sulfide resins (hereinafter, referred to as “PPS resins”), which have properties favorable as engineering plastics such as high heat resistance, high flame resistance, high rigidity, high chemical resistance and high electric insulating property, have been used mainly for injection molding in various applications such as electric and electronic parts, mechanical parts and auto-parts. However, PPS resins are not sufficiently high in toughness, compared to other engineering plastics such as polyamide resins. For that reason, PPS resins have been used mostly in combination with a reinforcing agent such as glass fiber for improvement in strength.
However, in recent trend for reduction in weight and improvement in surface smoothness, there is increasing demanded for non-reinforced materials also of PPS resins without any added reinforcement materials such as glass fiber and consequently, need for non-reinforced PPS material superior in toughness.
For improvement in toughness of non-reinforced PPS materials, known is a PPS resin composition containing a polyamide resin. For example, as disclosed in Japanese Patent application Laid-Open No. sho53-69255, Japanese Patent application Laid-Open No. Hei6-49356, many studies aimed at improving toughness of PPS resin by blending it with a high-toughness material are now in progress. If PPS and polyamide are compatible with each other uniformly, as sugar is dissolved in water, it is possible to achieve the object by the method disclosed. However, it is known that PPS and polyamide are hardly compatible with each other and only 4,6 nylon is compatible with PPS at a temperature of 300° C. or higher, but phase separation occurs when the blend is cooled (J. MACROMOL. SCI. PHYS., B41 (3), 407-418 (2002), Jung-Bum An, Takeshi Suzuki, Toshiaki Ougizawa, Takeshi Inoue, Kenji Mitamura and Kazuo Kawanishi). As it is well recognized, a blend of polymer and elastomer shows remarkably improved physical properties, when they are compatibilized, but, such a favorable combination with the PPS resin is not known. Thus, blend with other elastomer is not an effective means of improving strength and other physical properties and may instead impair favorable properties of the PPS resin such as high modulus and high combustion resistance.
On the other hand, Japanese Patent application Laid-Open No. Hei9-291213 and Japanese Patent application Laid-Open No. sho62-197422 disclose oxidatively crosslinked PPS resins resistant to weld cracking and superior in mechanical strength, but they are still not satisfactory in toughness such as tensile elongation and impact strength. In addition, the oxidative crosslinking treatment has a problem that it is difficult to apply it to applications demanding continuous production of molded articles, for example by extrusion molding.
In addition, if a PPS resin composition is used in production of a transferring belt in the electrophotographic application, it is necessary to make the resin's conductivity uniform in the semiconductor range by adding a conductive substance such as carbon, but PPS resins often prohibit favorable dispersion of carbon, unfavorably leading to change in the dispersion state of carbon during extrusion molding and uneven distribution of conductivity. A transferring belt having uneven distribution of conductivity has a problem of filming during long-term printing.
Further, because various components are solubilized and dispersed not sufficiently uniformly in conventional PPS resin compositions, molded articles prepared by using such a composition showed great change in glass transition temperature before and after molding treatment. Thus, the wastes from molded article or those generated in the production process could not be used as raw materials for recycling.
By the way, known as the methods for producing a polymer composition by blending two or more compounds containing at least one kind of polymer are batch-wise production methods of using a batch-wise apparatus such as Banbury mixer, kneader or roll and continuous production methods of using a continuous apparatus such as uniaxial kneading machine, biaxial kneading machine, or mill kneading machine. Polymer compositions such as a blend of polymer and compounding ingredient or plural polymers, and polymer alloys are produced in these apparatuses, as they are blended under elongation flow and shearing flow.
However even if a polymer composition is produced in a known kneading machine or by a kneading method, it was difficult to mix the components constituting the polymer composition uniformly, in particular to disperse the additives contained in the polymer composition uniformly. It was thus not possible to control physical properties of a molded article produced by using the polymer composition obtained to a level satisfying requirements needed in its application.
For example in production of a semiconductive polymer by dispersing a conductive substance in an insulative polymer, it was difficult to reduce unevenness in resistance of the resulting semiconductive polymer to a satisfactory level. In production of a polymer alloy by blending two kinds of polymers less compatible with each other for example, it was difficult to control diameters of polymer particles dispersed in the polymer alloy to less than 1 μm.